Synchronized Deformation Monitoring in Laser Cleaning: an Application for Cultural Heritage Conservation

Abstract

The photo-induced effects generated upon laser cleaning result to the removal of unwanted material, still transient deformation and damage on the surface and the structure of the materials can be also occurred. It is herein presented a laser-based workstation to monitor deformation and to evaluate any damage potentially induced by laser cleaning processes in a non-destructive and on-line methodology. An all-optics laser geometry, which allows the alignment of the ablation beam and the monitoring system, is enabled. On-line surface monitoring of photomechanical effects is performed through the acquisition of surface condition and its relevant displacement associated to the synchronously performed laser cleaning procedure. Surface condition is traced by interference generated patterns expressed in spatial coordinates and their alterations throughout the cleaning process. Transient deformation, damage, successful or successful intervention is deduced upon comparison of the last to the initial-reference position of the surface points. The all-optics laser-workstation aims to respond to the increasing demand of controlled interventions satisfying safety regulations and preventive measures to be taken on time. As a proof of application principle infrared (IR) laser-cleaning in the removal of varnish from wooden objects monitored with the synchronized coherent interferometry